The present invention relates to bookbinding machines in general, and more particularly to improvements in apparatus for attaching end papers, cover lining sheets or other types of sheets to adhesive-coated edge faces of groups of leaves (e.g., groups of gathered signatures) in a bookbinding machine.
End papers, cover lining sheets or analogous components are attached to groups of gathered leaves while the groups are held by equally spaced grippers or tongs and move in the bookbinding machine along a straight portion of an endless path which is defined by a conveyor for the grippers. One edge face of each group is coated with a suitable adhesive, and each sheet must be properly oriented with respect to the corresponding group of leaves in order to insure that a predetermined portion of the sheet is bonded to the associated group. The machine normally further comprises devices which treat the groups of leaves during transport along or ahead of the aforementioned portion of the endless path; such devices may include a paster which applies a film of adhesive to a selected edge face of each group of leaves. As a rule, the machine further comprises means for urging properly oriented sheets against the films of adhesive at the edge faces of adjacent groups to insure that the sheets are properly bonded to such groups; the pressing means may but need not be heated, depending on the nature of the adhesive. The sheets are withdrawn from a magazine by a suitable feeding device.
In certain presently known bookbinding machines, the feeding device includes a suction head or analogous means for withdrawing discrete sheets from the magazine and an upwardly sloping conveyor which transports successive sheets along an inclined path onto a pressing member which is mounted at a level below the aforementioned straight portion of the path for the grippers and is movable in the direction of movement of the adjacent gripper, counter to such direction as well as up and down so that a sheet which rests on the pressing member is attached to the adjacent group while the pressing member moves upwardly. The pressing member includes means for centering the sheet thereon in order to insure that the sheet is properly oriented before it comes into contact with the film of adhesive on the respective group. The machine comprises a conveyor which moves the pressing member back and forth along a second path which is located at a level below and is parallel to the straight portion of the path for the grippers. The centering means is active during upward movement of the pressing member. Reference may be had to Swiss Pat. No. 475,098.
A drawback of the just described conventional apparatus is that the pressing member cannot be moved at a high speed because the orientation of sheets thereon takes place while the pressing member moves upwardly toward the adjacent gripper. Moreover, the pressing member must move back to a starting position before it receives a fresh sheet. Consequently, the output of the bookbinding machine is relatively low because the speed of grippers cannot exceed the speed of the pressing member. In the absence of such pressing member, the machine could turn out a much larger number of books, brochures, pamphlets or the like per unit of time.